Many portable electronic systems, such as laptop computers and cellular phones, utilize rechargeable battery packs to receive their power. Such battery packs have the advantage that they are portable, relatively weight efficient, and can be charged and discharged many times. However, due to certain characteristics of existing rechargeable battery packs, an accurate indication of the remaining charge is very difficult to determine.
As can be appreciated, it is very desirable to be able to accurately determine the remaining operating life of a rechargeable battery pack used in a system such as a laptop computer. This enables a user to get maximum use out of the rechargeable battery pack. This is especially critical when the remaining energy of the rechargeable battery pack falls below the operating threshold of the computer. A user would ideally want to be able to safely shut down the computer prior thereto, thereby preventing any potential loss of information.
The amount of the charge flowing into and out of the rechargeable battery pack during charging and discharging are parameters that can be monitored and used to calculate the remaining charge of a rechargeable battery. As can be further appreciated, the more accurately and reliably this information is measured and accumulated, the more accurate the calculation of the remaining charge of the rechargeable battery.
In addition to the discharge that occurs during regular use of a rechargeable battery pack, a rechargeable battery pack will also have a certain amount of self-discharge when not in use. This self-discharge is very difficult to account for when calculating the remaining charge of the rechargeable battery. In existing rechargeable battery packs, the amount of time the rechargeable battery pack is not being used is very difficult to determine. Additionally, the amount of self-discharge of a rechargeable battery will fluctuate with varying temperatures. As can be appreciated, a problem with existing rechargeable battery packs is that they do not take into account the self-discharge of the battery, nor do they take into account the varying temperatures when calculating the remaining charge of the rechargeable battery.
Therefore, there is a need for a rechargeable battery pack having accurate and reliable gas gauge circuitry that incorporates self-discharge accounting to determine the remaining operating life of the rechargeable battery pack.